The present invention relates to a microfluid driving device, especially to a non-contact pneumatic microfluid driving device comprising an external servo system and a chip carrying a microfluid driving platform.
The xe2x80x9cbiochipxe2x80x9d which is able to automatically operate the nucleic acid sample processing and the testing of base series has been developing in all countries the world. In these biochips, the microfluid driving system that drives microfluid that contains samples of biochemical agents to move inside microfluidic channels is one of the most important equipments. The question of how to easily control fluid movement and avoid the cross pollution of the sample or the biochemical agents with the driving system, as become a question of interest.
The microfluid driving system that are known to the public may be divided into three classes. They are the on-chip mechanical micropump, the on-chip electrokinetic micropump and the external servo system. Descriptions thereof will be given as follows:
The on-chip mechanical micropump is an embedded mechanical micropump prepared directly in a chip with the micromachining technology. In an on-chip mechanical micropump, there must have moveable parts in the chip. The electrostatically driven diaphragm micropump invented by Roland Zyngerle et al., U.S. Pat. No. 5,529,456 is one example.
In such a micropump, the micropump includes a pressure chamber. An intermittent electrostatic driving force is generated between the two-layer structure of the pressure chamber and the two one-way passive check valves positioned in the microfluidic channel are driven in turns. Such an operation generates a pumping force to the microfluid. The working flow rate of the micropump is about 350 xcexcl/min.
The micromachined peristaltic pump invented by Frnak T. Hartley, U.S. Pat. No. 5,705,018 disclosed to another structure. In this invention, a series of flexible conductive strips are provided along the inner wall of the microchannel which is provided in a chip. When voltage pulses pass over the microchannel, the flexible conductive strips are pulled upward by electrostatic force generated in turn. A peristaltic phenomena will thus take place. The microfluid in the microchannel may thus be driven by the driving force of the strips. Working flow rate of this invention is about 100 xcexcl/min.
In such a mechanical microfluid driving system provided with moveable elements and with a complicated structure, it is very difficult to clean up all residuals of samples or biochemical reagents of another experiment. As a result, most microfluid driving systems for biochips shall be disposable. However, both the embedded rotational micropump and the embedded peristaltic micropump have complicated process of manufacture and expensive customer design components, which made the preparation costs of the micropump relatively high. Such a micropump is not suited in disposable chips.
In addition to that, the mechanical micropumps are generally prepared with membranes, valves or gears which are driven by relatively higher powers, such as electric, magnetic or thermal powers. Such a requirement involves complicated structure, complicated operations and higher costs. Furthermore, it is even more difficult to prepare a pump or pump module that provides driving forces back and forth in the microchannel.
The on-chip electrokinetic micropump is a non-mechanical micropump. Inside the pump there are no moveable elements. Operations of such a micropump may be carried on by electro-osmosis (EO), electro-hydrodynamic (EHD) or electrophoresis (EP).
In 1997 Peter J. Zanzucchi et al. disclosed an apparatus and methods for controlling fluid flow in microchannels in their U.S. Pat. No. 5,632,876. This invention related to a microfluid driving system employing the combination of the electro-osmosis power and the electro-hydrodynamic power. The invented apparatus comprises a microchannel provided in a chip and two pairs of electrodes, totally four, are arranged in the microchannel in turn. A pair of electrodes are deeply put in the microchannel. When high voltage is applied to the electrodes, fluid adjacent to the electrodes will be carried in a direction reverse to the direction of the electrical current. An EHD pumping is thus accomplished. Electrodes of the other pair are positioned at both sides from the first pair and contact the walls of the microchannel. When a high voltage is applied to these electrodes, the walls of the microchannel are first electrically charged and charged carriers are accumulated. Electro-osmosis is thus generated in the charge-containing particles in the microfluid and drives the microfluid to flow, carrying out the so-called EO pumping. In this apparatus two kinds of electrode-generated powers are used to generate pumping forces to the microfluid. The microfluid may thus be driven forward, backward or halt inside the microchannel by controlling the ratio of the EHD pumping force and the EO pumping force.
Paul C. H. Li and D. Jed Harrison disclosed a microfluid driving system with the combination of the electro-osmosis power and the electrophoresis power in their article entitled xe2x80x9cTransport, manipulation, and reaction of biological cells on-chip using electrokinetic effects (Anal. Chem. 1997, 69,m 1564-1568). In this driving system, electro-osmosis force generators and electrophoresis force generators are arranged in turn in the microchannel. The differences between an electro-osmosis force and an electrophoresis force adjacent to each other, cells in a microfluid may be easily driven to move, direction-turning or even classification. However, the objects moved by the electro-osmosis force or the electrophoresis force are the charge-containing particles in the solution, not the solution itself. As a result, these inventions are not driving systems for microfluids, but rather, are driving systems for charged cells, such as canine erythrocyte et al., in a solution.
From the process point of view, the electrode micropump is simple in structure, low in manufacture cost but limited in application. First, inside the microchannel, solvent must be filled before anything may be driven. It is not possible to introduce samples or reagents into empty channels. Secondly, the distance that an EHD pump can drive a microfluid is limited. The objects that an EO pump or an EP pump drives are charge-containing particles in a microfluid, not the microfluid itself. Neither of these pumps provides satisfactory pumping effects. Working flow rate of these pumps is about 10 xcexcl/min. In addition, these pumps may only work in microchannels with tiny diameter, e.g., 100 xcexcm and a voltage difference of hundreds to thousands of volt must be generated within a short distance. High operation costs are thus caused. The EHD pump can only be applied to non-polar organic solvents and the EO pump and the EP pump can only be applied polar solvents. The driving efficiency of the pumps is highly influenced by the concentration of ions in the solution. When the ion concentration of the solution varies during the reaction, driving of the solution will become more difficult to control.
When the microfluid is driven by an external servo system, there is no need to provide any active element in the chip containing the microchannel. Such a chip may be prepared under a lower cost easily. The external servo system is not directly connected to the samples or the reagents and maybe used repeatedly. The problem is the interface between the servo system and the chip, the xe2x80x9csystem-to-chip interfacexe2x80x9d. How to connect transmission pipes of carrier fluids, which are in normal sizes, to the microchannels of the chip, which are miniature in size, will become a task to be achieved by using a series of micro fabrication technologies. If the problem of the system-to-chip interface can be solved, the combination of an external servo system and a disposable biochip which contains no active components will be highly feasible in the preparation of the microfluid driving system.
It is thus necessary to provide a novel microfluid driving device that provides driving forces to microfluid such that the microfluid may proceed inside a microchannel.
It is also necessary to provide a microfluid driving device that is simplified and is easy to prepare.
It is also necessary to provide a microfluid driving device with an external servo system to drive the bi-directional movement of microfluid in a microchannel.
The objective of this invention is to provide a novel microfluid driving device that provides driving forces to microfluid such that the microfluid may proceed inside a microchannel.
Another objective of this invention is to provide a microfluid driving device that is simplified and is easy to prepare.
Another objective of this invention is to provide a microfluid driving device with an external servo system to drive the bi-directional movement of microfluid in a microchannel.
Another objective of this invention is to provide a bi-directional driving method for microfluid.
Another objective of this invention is to provide a novel bi-directional driving system for microfluid.
According to this invention, a microfluid driving device is provided. The microfluid driving device of this invention comprises microfluid driving platform prepared in a chip, which platform comprises at least two miniature Venturi pumps, at least one microchannel and optionally micro mixers or micro reactors in said microchannel; an external pneumatic flow supply and control module that provides selectively different air flows; and an interface device connecting said microfluid driving platform and said external pneumatic flow supply and control module. The air flows supplied by said the pneumatic flow supply and control module are supplied under selected flow rates and frequencies to said at least two Venturi pumps through said interface device, such that the microfluid inside said microchannel may be driven forward or backward or halt and the transportation, mixing and reaction of the microfluid may be accomplished.
These and other objectives and advantages of this invention may be clearly understood from the detailed description by referring to the following drawings.